This invention relates to semiconductor laser diodes. More specifically, it relates to laser diode modules which may include a plurality of semiconductor laser diodes. Such laser diodes are capable of generating a relatively high beam output for their size and are used in such applications as fiber optic communications and laser surgery. Typically, such semiconductor diode lasers emit energy in the wavelength range of 0.805 to 1.55 micrometers for efficient coupling to fiber optics. For a background discussion of such semiconductor diode lasers see Laser Focus World, August, 1992, pgs. 79 et seq. One type of a laser diode suitable for use with the present invention is disclosed in U.S. Pat. Nos. 4,860,298 and 4,985,897 both to Dan Botez et al. hereby incorporated by reference. The laser diode there disclosed typically comprise between twenty to forty laser elements and having a size of 100 microns thick by 0.5 millimeters wide by 1.0 millimeters long. Such modules are capable of generating in excess of 15 watts. These devices are capable of many applications, but a principal problem with their use is the dissipation of heat, which is considerable at this relatively high output to size ratio.
Typically, the laser outputs are concentrated into a beam focused by a lens system into a single beam which may, if desired, thereafter be coupled to a fiber optic cable or similar device. Details of the lasers and the means for optically focusing the beams are disclosed in the aforementioned Botez et al. patents, although they are discussed herein as necessary to an understanding of the invention. Such devices typically have a current input of between 0.5 and ten amps or higher and can create an output of between 0.2 and ten watts or more of optical power. One limiting parameter on light output is heat build-up. Without efficient cooling, the optical power output decreases rather dramatically as temperature increases. As a rule of thumb, if ten watts of optical power are created, there are approximately ten watts of heat which must be dissipated.
Previous designs have been able to obtain only approximately 200 milliwatts of optical power without some form of cooling. Thus, the laser module according to the present invention is capable of optical power orders of magnitude greater than the prior art. Such a high optical output device has many applications if it can be appropriately packaged, focused and cooled at a reasonable cost. Some of these applications include marking substrates with alpha-numeric information, medical applications, laser type-setting, desktop manufacturing, manufacture of semi-conductor devices and many others. In short, a high output, low-cost laser module is desirable and would be well received in the marketplace.
As indicated, the prior art has not heretofore been capable of such high output without significant additional expense to add on cooling and lens systems external to the module. It is an object of the present invention to overcome these disadvantages by incorporating both into the module in a simple and inexpensive manner.
Existing lower power (less than 1 watt) laser diodes are currently available in three general packaging formats. The most basic is an open heat sink package, usually in the form of a C-mount. This format is intended for custom integration with optical lens coupling and cooling systems which must be added on to the laser module. A second form of packaging, cylindrical packaging such as the TO series, is also a common format used where coupling to fiber optics is required but cooling is not required or can be satisfactorily accomplished by mounting the device to a cold (usually metallic) surface.
Where higher power output is required a high heat load (HHL) package is commonly used. The HHL is a rectangular package often provided with fiber coupling. The package may incorporate thermoelectric cooling, but usually requires mounting to an external cooling device or providing a submount that provides for micro-channel cooling, impingement cooling or back cooling. All of these high efficiency cooling and mounting techniques require further integration into a package that does not by itself provide for fiber coupling. In short, the lack of a unified design results in excessive cost, undue size and thereby limits the usefulness of the device.
In order to provide for practical application of high powered laser diodes, it is necessary to provide efficient cooling and fiber optic coupling in a low-cost integrated package. It is necessary to overcome the inherent difficulties of the HHL rectangular package which does not allow for low-cost fiber optic coupling and which often requires electrical connections to be made by soldering to a glass insulated feedthrough. Furthermore, such packaging is inherently expensive and difficult to interface. The present invention overcomes these problems by packaging the laser in a cylindrical form that incorporates direct water cooling of the laser chip, integrated fiber optic coupling and easy to connect and disconnect electrical leads.
It is accordingly an object of the present invention to provide a high-powered laser diode module in a cylindrical, but modular building block form. It is a further object to provide such a module with a quick connect/disconnect mounting feature and with integrated fiber optic coupling. A further object of the invention is to provide such a module with integrated liquid cooling and simple alignment features whereby the module can be designed and implemented with inexpensive materials and low-production costs to facilitate widespread application of this technology.
These and other objects of the invention will be apparent from the remaining portion of this specification.